Emergency braking control strategy based on safety distance model

Abstract

The present invention relates to the field of assisted driving technology, and specifically to an emergency braking control strategy based on a safety distance model; the strategy comprises dividing the relative distance intervals between two vehicles, a safety distance model, modeling the driver's reaction time, and dividing the danger levels, and covers the perception, decision-making, and control processes during the operation of the AEB system. In the process of dividing the relative distance intervals between the two vehicles, in order to reduce the damage to the driver caused by excessive braking intensity, the relative distance between the two vehicles is divided into four intervals. When establishing the safety distance model, the driver's driving style and braking comfort are taken into account while ensuring safety. The parking safety distance and the braking deceleration during graded braking are reasonably set. In the process of modeling the driver's reaction time, the influence of speed on it is considered. The present invention fully considers the safety, comfort, and diversity of the emergency braking system during operation.

Description

Technical Field

[0001] The present invention relates to the field of assisted driving technology, and in particular to an emergency braking control strategy based on a safety distance model. Background Art

[0002] Intelligent vehicles are becoming a mainstream trend in the automotive industry. From anti-lock braking systems to driver assistance systems, improving vehicle safety has been a key focus of automotive development. Longitudinal control in intelligent vehicles involves aligning the actual vehicle speed with the desired speed to ensure safety and stability. This control is typically achieved by switching between the accelerator and brake pedals. These controls are typically manually controlled by the driver. However, due to the driver's limited precision, reaction time, and close dependence on the driver's current driving state, this increases the risk of accidents in emergency situations. Consequently, automated longitudinal control technologies have emerged. These technologies not only reduce the driver's workload but also allow for proactive judgment and action in the event of driver error. Autonomous Emergency Braking (AEB) is a key technology, playing a significant role in reducing collisions. According to research from Euro NCAP, the European New Car Assessment Program, AEB can prevent 27% of collisions.

[0003] However, some current AEB systems have problems such as frequent braking and poor driver acceptance due to a single braking strategy. Summary of the Invention

[0004] To address the shortcomings of existing AEB systems, the present invention provides an emergency braking control strategy based on a safety distance model, which takes into account driving style and comfort while ensuring safety, and has a quick response, good braking effect, and infrequent braking.

[0005] The emergency braking control strategy based on the safety distance model is implemented by the following steps:

[0006] Step 1: Establish a three-level safety distance model:

[0007] The AEB system is designed with three levels of braking control based on length and distance. The first-level partial braking distance is the driver's braking distance during normal emergency braking at the 50th percentile driver's deceleration value, the second-level partial braking distance is the shortest driver braking distance at the maximum braking deceleration, and the third-level full braking distance is the shortest vehicle braking distance at the maximum braking deceleration.

[0008] Under CCRs working conditions, the first-level partial braking safety distance is calculated as follows:

[0009]

[0010] Under CCRs working conditions, the secondary partial braking safety distance is calculated as follows:

[0011]

[0012] Under CCRs conditions, the third-level full braking safety distance is calculated as follows:

[0013]

[0014] Under CCRm working condition, the first-stage partial braking safety distance is calculated as follows:

[0015]

[0016] Under the CCRm working condition, the secondary partial braking safety distance is calculated as follows:

[0017]

[0018] Under the CCRm condition, the third-level full braking safety distance is calculated as follows:

[0019]

[0020] Under the CCRb1 working condition, the first-stage partial braking safety distance is calculated as follows:

[0021]

[0022] Under the CCRb1 working condition, the secondary partial braking safety distance is calculated as follows:

[0023]

[0024] Under the CCRb1 working condition, the third-level full braking safety distance is calculated as follows:

[0025]

[0026] Under the CCRb2 working condition, the first-stage partial braking safety distance is calculated as follows:

[0027]

[0028] Under the CCRb2 working condition, the secondary partial braking safety distance is calculated as follows:

[0029]

[0030] Under the CCRb2 working condition, the third-level full braking safety distance is calculated as follows:

[0031]

[0032] Among them, v1 is the vehicle speed (m / s), v obj is the target vehicle speed (m / s), v rel is the relative speed of the two vehicles (m / s), a obj is the target vehicle deceleration (m / s 2 ), a b_m is the maximum deceleration (m / s 2 ), a b_50％ The acceptable braking deceleration for the 50th percentile driver (m / s 2 ), a rel_m =a b_m -a obj ,a rel_50％ =a b_50％ -a obj , t b is the braking delay time, t1 is the driver's reaction time, d x_0 is the safe stopping distance and {x|x∈c,g,r}, where c represents a conservative driver, g represents a normal driver, and r represents an aggressive driver;

[0033] Step 2: Develop a hierarchical control strategy:

[0034] Situations greater than the first-level partial braking safety distance are classified as safe, and the AEB system does not need to intervene at this time; situations less than the first-level partial braking safety distance and greater than the second-level partial braking safety distance are classified as first-level danger, and the AEB system is required to perform first-level partial braking according to the set first-level partial braking deceleration; situations less than the second-level partial braking safety distance and greater than the third-level full braking safety distance are classified as second-level danger, and the AEB system is required to perform second-level partial braking according to the set second-level partial braking deceleration; situations less than the third-level full braking safety distance are classified as third-level danger, and the AEB system is required to perform full braking according to the set full braking deceleration;

[0035] Step 3: converting the braking deceleration determined by the AEB system in step 2 into a brake master cylinder pressure and applying it to the vehicle;

[0036] The brake master cylinder pressure P b Calculate as follows:

[0037] F b =K b P b

[0038] Among them, K bIndicates the ratio of braking force to brake master cylinder pressure, F b The braking force of the vehicle brake,

[0039] Calculate as follows:

[0040] Ma exp =F b +∑F

[0041] Where M represents the vehicle mass, a exp represents the expected deceleration, i.e., the braking deceleration determined by the AEB system in step 3. ∑F represents the driving resistance of the vehicle when not braking, which is calculated as follows:

[0042]

[0043] Where A represents the frontal area of ​​the vehicle, C D represents the air resistance coefficient, ρ represents the air density, v represents the vehicle speed, g represents the acceleration due to gravity, and f represents the rolling resistance coefficient.

[0044] In step 2, for a conservative driver, the AEB system performs a partial braking deceleration of a. c_par Select 2.8m / s 2 , deceleration a of the secondary partial braking c_part2 Select 5.7m / s 2 , deceleration a of full braking c_max Select 8m / s 2 ;

[0045] For a normal driver, the AEB system performs a partial braking deceleration of g_part1 Select 3.7m / s 2 , deceleration a of the secondary partial braking g_part2 Select 6.5m / s 2 , deceleration a of full braking g_max Select 8m / s 2 ;

[0046] For aggressive drivers, the AEB system performs partial braking at a deceleration of r_part1 Select 4.1m / s 2 , deceleration a of the secondary partial braking r_part2 Select 7m / s 2 , deceleration a of full braking r_max Select 8m / s 2 .

[0047] In the step three, the master brake cylinder pressure is adjusted by a PID controller according to the obtained master brake cylinder pressure.

[0048] Beneficial effects of the present invention:

[0049] In the process of establishing the speed-distance exponential following model, the present invention fully considers the influence of speed and distance on the expected acceleration, and the exponential function form adopted can reflect the asymmetry of the driver's acceleration and braking behaviors.

[0050] In the process of establishing the limited distance perception model, the present invention fully considers the physiological characteristics of the driver, can reflect the error mechanism of human drivers to a certain extent, improves the anthropomorphism of the car-following model, and provides a reference for the design of intelligent assistance systems.

[0051] The present invention fully considers the impact of driving style on the driver's following behavior. Driving style not only affects the driver's decision-making process, but is also fully reflected in aspects such as distance perception and risk assessment. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the following briefly introduces the drawings used in the description of the embodiments of the present invention. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the contents of the embodiments of the present invention and these drawings without paying any creative work.

[0053] Figure 1 is a flow chart of the present invention;

[0054] Figure 2 This is a schematic diagram of the area division of the actual distance between two vehicles based on the vehicle braking process of the present invention;

[0055] Figure 3 This is a flowchart of the Euro-NCAP test condition judgment of the present invention;

[0056] Figure 4 A graph showing the relationship between the driver's braking reaction time and the vehicle's speed according to the present invention;

[0057] Figure 5 This is a schematic diagram of the graded braking strategy of the present invention. DETAILED DESCRIPTION

[0058] The present invention will be further described in detail below with reference to the accompanying drawings and examples. It will be understood that the specific embodiments described herein are intended only to illustrate the present invention and are not intended to limit the present invention. It should also be noted that, for ease of description, the accompanying drawings only illustrate portions relevant to the present invention, not all structures.

[0059] Example 1

[0060] The emergency braking control strategy based on the safety distance model is implemented through the following process, including dividing the relative distance interval between the two vehicles, the safety distance model, driver reaction time modeling, hazard level classification, and controller design, covering the perception, decision-making and control processes during the AEB operation.

[0061] The relative distance interval division method between two vehicles is used to formulate a hierarchical control strategy; the safety distance model is used to determine the safe distance under different operating conditions; the driver reaction time model is used to determine the driver's reaction time and then calculate the safe distance; the danger level classification is used to set the appropriate braking deceleration for drivers with different driving styles; and the controller is designed to convert the desired deceleration into the brake master cylinder pressure.

[0062] The specific steps of this embodiment are as follows:

[0063] Step 1: Divide the relative distance between the two vehicles:

[0064] In order to build a safety distance model, it is first necessary to analyze the emergency braking process under normal vehicle driving conditions. During the braking process, a normal vehicle will first experience the driver's reaction time and the lag time of the braking system before starting emergency braking. When the actual distance is less than the shortest vehicle braking distance, a collision will be inevitable, so braking measures should be taken before this. The present invention uses distance as a judgment condition, and considers the distance traveled by the vehicle during the driver's reaction stage on the basis of the shortest vehicle braking distance, as well as the shortest driver braking distance required while considering the driver's reaction time and the driver's acceptable braking intensity. After defining these three distances, the relative distance between the two vehicles can be divided into four areas; in the division process, the maximum braking intensity of the vehicle, the braking intensity generally accepted by the driver, and the driver's reaction time are considered, and the boundary distance of each interval is calculated separately;

[0065] Step 2: Establish a safe distance model:

[0066] A safety distance model for the system was established based on AEB testing regulations. The modeling process considered the impact of vehicle speed on driver reaction time, and a linear fit was performed on the relationship between driver reaction time and vehicle speed. To prevent premature intervention of the emergency braking system, the driver's braking distance for normal emergency braking was calculated with reference to the emergency braking deceleration law table. This was used as the safety distance for first-level partial braking. The shortest driver braking distance at maximum braking deceleration was used as the safety distance for second-level partial braking. The shortest vehicle braking distance at maximum braking deceleration was used as the safety distance for third-level full braking. Different driver driving habits were considered in the modeling process, and the safe stopping distance was appropriately set.

[0067] Step 3: Develop a hierarchical control strategy:

[0068] Based on the safety distance model defined in step 2, a quantitative judgment of the current danger level can be made. After the sensor measures the actual distance between the two vehicles, it will be compared with the critical distance calculated by the safety distance model based on the current situation. The braking intensity for different distance intervals will be reasonably set based on the emergency braking deceleration law table to determine the current danger level. Gradual braking will be performed according to the braking intensity set for different danger levels. Different braking intensities will be set for drivers with different driving styles based on the emergency braking deceleration law table during the graded braking process, thus achieving three-level braking control.

[0069] Step 4: Design the controller:

[0070] The first-stage partial deceleration, second-stage partial deceleration, and full braking deceleration, determined by the hazard level, cannot be directly applied to the vehicle. Therefore, an inverse longitudinal dynamics model is required to convert the desired deceleration into brake master cylinder pressure, which is then applied to the vehicle and used as a feedforward controller. Considering the unmodeled dynamics that cannot be modeled during the feedforward controller design process, a PID controller is designed for feedback correction and as a feedback controller.

[0071] Example 2

[0072] Combine Figures 1 to 5 This embodiment is an example of the emergency braking control strategy based on the safety distance model described in the first embodiment: the flowchart of the emergency braking system based on the safety distance model is as follows: Figure 1 As shown, data acquisition is achieved through sensors to detect the relative speed and relative distance between two vehicles, which are used to calculate the safety distance model; the safety distance model is used to calculate the safety distance under different working conditions and compare it with the actual relative distance to determine the danger level; the danger level classification is used to determine the braking deceleration; the controller is designed to convert the braking deceleration obtained by the braking strategy into braking pressure applied to the vehicle; the method includes the following steps:

[0073] Step 1: Divide the relative distance between the two vehicles:

[0074] For the emergency braking process, t1 is defined as the driver's reaction time, that is, the time from the driver discovering the obstacle signal to the time the driver touches the brake pedal. During the t1 stage, the brake pedal force F p and braking deceleration a b are all 0; t2 is defined as the braking system reaction time, that is, from the time the foot is stepped on the brake pedal to the time the braking system starts to work until the braking deceleration a bThe time required to reach the maximum; the t2 stage is further divided into two stages, t'2 and t'2, wherein the t'2 stage is the time for the brake to eliminate the idle stroke, which is used to establish sufficient line pressure and overcome the mechanical clearance inside the brake system, a b The braking force increases from the moment the driver steps on the pedal to the moment the brake friction pair begins to engage until the braking deceleration reaches its maximum. t3 is defined as the duration of continuous braking, during which the braking deceleration remains at its maximum value until the vehicle stops.

[0075] The distance s traveled by the car within the driver's reaction time t1 t1 Calculate as follows:

[0076] s t1 =v0t1 (1)

[0077] Where v0 is the initial velocity of the vehicle;

[0078] At the beginning of the brake operation, the distance s′ traveled by the vehicle within the time t′2 when the brake eliminates the idle travel t2 Calculate as follows:

[0079] s′ t2 =v0t′2 (2)

[0080] In the braking force growth phase t″2, let the deceleration rate be constant. The distance traveled by the car in this phase is s″ t2 Calculate as follows:

[0081]

[0082] Among them, a b_m is the maximum braking deceleration in stage t″2;

[0083] During the brake action phase, that is, within t2, the vehicle braking distance s t2 Calculate as follows:

[0084]

[0085] In the t3 stage, the car has an initial speed of The final velocity is 0 and the deceleration is a b_m The distance s traveled by the car in this stage is calculated as follows: t3 :

[0086]

[0087] Driver braking distance s dThe vehicle travel distance includes the three time periods of driver reaction time, braking system reaction time and continuous braking time; the vehicle braking distance s v It refers to the distance traveled by the car from the time the driver starts to press the brake pedal to the time the vehicle comes to a complete stop, including the braking system reaction time and the distance traveled by the car during the continuous braking time. The calculation formula is as follows:

[0088] s d =s t1 +s t2 +s t3 (6)

[0089] s v =s t2 +s t3 (7)

[0090] Considering the value of the maximum deceleration, the vertical distance between the front end of the host vehicle and the rear end of the target vehicle is divided into four parts: greater than the normal emergency braking driver braking distance, between the normal emergency braking driver braking distance and the shortest driver braking distance, between the shortest driver braking distance and the shortest vehicle braking distance, and less than the shortest vehicle braking distance; among which:

[0091] The driver's braking distance s for normal emergency braking d1 Calculate as follows:

[0092]

[0093] The shortest driver braking distance s d2 Calculate as follows:

[0094]

[0095] The shortest vehicle braking distance s v Calculate as follows:

[0096]

[0097] The a b_50％ The deceleration acceptable to the 50th percentile driver;

[0098] The intervals obtained by the above calculation method are as follows Figure 2 shown.

[0099] Step 2: Establish a safe distance model:

[0100] The safety distance of the automatic emergency braking system (AEB) system includes a time distance and a length distance. The control strategy of the present invention is based on the length distance and is designed as a three-level braking control. To prevent the AEB system from intervening prematurely, the emergency braking deceleration law table is referenced. The driver's braking distance during normal emergency braking when braking at the 50th percentile driver's deceleration value is used as the first-level partial braking safety distance, the shortest driver braking distance when braking at the maximum braking deceleration value is used as the second-level partial braking safety distance, and the shortest vehicle braking distance when braking at the maximum braking deceleration value is used as the third-level full braking safety distance.

[0101] During the driving process, the speed and distance of the target vehicle are obtained according to the sensor, and the speed and acceleration of the own vehicle are obtained according to the own sensor. When the speed of the target vehicle is less than the speed of the own vehicle, the working condition is judged. According to the Euro NCAP test standard, when the speed of the own vehicle is not zero and the speed of the target vehicle is zero, it is judged to be the CCRs working condition. When the speed of the own vehicle is not zero and the speed of the target vehicle is constant, it is judged to be the CCRm working condition. When the target vehicle speed is decreasing, it is the CCRb working condition. According to the deceleration of the target vehicle, it can be divided into two situations. CCRb1 is the working condition of the target vehicle under normal braking and deceleration. CCRb2 is the working condition of the target vehicle under emergency braking and stopping before the own vehicle. The judgment process is as follows Figure 3 As shown. Therefore, the following safety distance model is established for the verification conditions in Euro-NCAP:

[0102] Under CCRs working conditions, the first-level partial braking safety distance is calculated as follows:

[0103]

[0104] Under CCRs working conditions, the secondary partial braking safety distance is calculated as follows:

[0105]

[0106] Under CCRs working conditions, the full braking safety distance is calculated as follows:

[0107]

[0108] Under CCRm working condition, the first-stage partial braking safety distance is calculated as follows:

[0109]

[0110] Under the CCRm working condition, the secondary partial braking safety distance is calculated as follows:

[0111]

[0112] Under CCRm working condition, the full braking safety distance is calculated as follows:

[0113]

[0114] Under the CCRb1 working condition, the first-stage partial braking safety distance is calculated as follows:

[0115]

[0116] Under the CCRb1 working condition, the secondary partial braking safety distance is calculated as follows:

[0117]

[0118] Under CCRb1 working condition, the full braking safety distance is calculated as follows:

[0119]

[0120] Under the CCRb2 working condition, the first-stage partial braking safety distance is calculated as follows:

[0121]

[0122] Under the CCRb2 working condition, the secondary partial braking safety distance is calculated as follows:

[0123]

[0124] Under CCRb2 working condition, the full braking safety distance is calculated as follows:

[0125]

[0126] Among them, v1 is the vehicle speed (m / s), v obj is the target vehicle speed (m / s), v rel is the relative speed of the two vehicles (m / s), a obj is the target vehicle deceleration (m / s 2 ), a b_m is the maximum deceleration (m / s 2 ), a b_50％ The acceptable braking deceleration for the 50th percentile driver (m / s 2 ), a rel_m =a b_m -a obj , a rel_50％ =a b_50％ -a obj , t b is the braking delay time (including the time to eliminate the brake pedal clearance and the linear increase of the braking deceleration, generally 0.1s, temporarily set to zero in simulation, and needs to be tested in actual application), t1 is the driver's reaction time, d x_0is the safe stopping distance and {x|x∈c,g,r}, where c represents a conservative driver, g represents a normal driver, r represents an aggressive driver, and d r_0 =2m,d g_0 =3.5m,d c_0 =5m;

[0127] As for the driver's braking reaction time, as the vehicle speed increases, the driver's reaction time tends to decrease. The relationship between the driver's braking reaction time and speed is fitted as follows: Figure 4 As shown;

[0128] Step 3: Develop a hierarchical control strategy:

[0129] Situations greater than the first-level partial braking safety distance are classified as safe, and the AEB system does not need to intervene at this time; situations less than the first-level partial braking safety distance and greater than the second-level partial braking safety distance are classified as first-level danger, and the AEB system is required to perform first-level partial braking according to the set first-level partial braking deceleration; situations less than the second-level partial braking safety distance and greater than the full braking safety distance are classified as second-level danger, and the AEB system is required to perform second-level partial braking according to the set second-level partial braking deceleration; situations less than the full braking safety distance are classified as third-level danger, and the AEB system is required to perform full braking according to the set full braking deceleration;

[0130] The controller receives the relative distance signal and outputs the desired acceleration after judging the danger level. There are four discrete states: maintaining the original speed, partial braking at level one, partial braking at level two, and full braking.

[0131] For conservative drivers, the AEB system performs partial braking at a deceleration of c_part1 Select 2.8m / s 2 , deceleration a of the secondary partial braking c_part2 Select 5.7m / s 2 , deceleration a of full braking c_max Select 8m / s 2 ;

[0132] For a normal driver, the AEB system performs a partial braking deceleration of g_part Select 3.7m / s 2 , deceleration a of the secondary partial braking g_part Select 6.5m / s 2 , deceleration a of full braking g_max Select 8m / s 2 ;

[0133] For aggressive drivers, the AEB system performs partial braking at a deceleration ofr_part1 Select 4.1m / s 2 , deceleration a of the secondary partial braking r_part Select 7m / s 2 , deceleration a of full braking r_max Select 8m / s 2 The selection of braking deceleration value refers to the statistical law of deceleration during emergency braking, as shown in Table 1.

[0134] Table 1

[0135]

[0136] AEB control strategy process is as follows Figure 5 If the sensor does not detect the target vehicle, the AEB system does not take any action and the car continues to drive; when the actual distance between the target vehicle and the host vehicle is less than the first-level partial braking safety distance, the first-level partial braking force is generated; when the actual distance is less than the second-level partial braking safety distance, the second-level partial braking force is generated; when the actual distance is less than the full braking safety distance, the system will help the driver reach the full braking force. After the system intervenes, it will continue to control the vehicle until the dangerous state is eliminated, that is, the actual distance is greater than the first-level partial braking safety distance.

[0137] Step 4: Design the brake master cylinder pressure PID controller:

[0138] The braking deceleration determined by the AEB system in step 3, i.e., the desired deceleration derived from the safety control strategy, is converted into brake master cylinder pressure through an inverse brake model and applied to the vehicle. An inverse brake system model is established and used as a feedforward controller. Considering the unmodeled dynamics, a PID controller is designed as a feedback controller.

[0139] The force analysis of the vehicle during normal driving on a straight road is as follows:

[0140]

[0141] Among them, ∑F represents the driving resistance of the vehicle when it is not braking, A represents the frontal area of ​​the vehicle, and C D represents the air resistance coefficient, ρ represents the air density, v represents the vehicle speed, M represents the vehicle mass, g represents the acceleration of gravity, and f represents the rolling resistance coefficient;

[0142] When the vehicle's braking intensity is low, the vehicle's brake force is equal to the ground braking force. However, when the braking intensity is high, the ground braking force will no longer increase due to the influence of the adhesion coefficient, while the brake force will increase. Therefore, in order to avoid the calculation inconvenience caused by the brake force exceeding the ground braking force, it is assumed that the vehicle's maximum braking force during braking is always less than the maximum ground braking force, so the brake pressure and braking force are directly proportional.

[0143] The brake master cylinder pressure P b Calculate as follows:

[0144] F b =K b P b (twenty four)

[0145] Among them, K b Indicates the ratio of braking force to brake master cylinder pressure, F b The braking force of the vehicle brake,

[0146] Calculate as follows:

[0147] Ma exp =F b +∑F (25)

[0148] Where M represents the vehicle mass, a exp represents the expected deceleration, i.e., the braking deceleration determined by the AEB system in step 3. ∑F represents the driving resistance of the vehicle when not braking, which is calculated as follows:

[0149]

[0150] Where A represents the frontal area of ​​the vehicle, C D represents the air resistance coefficient, ρ represents the air density, v represents the vehicle speed, g represents the acceleration of gravity, and f represents the rolling resistance coefficient;

[0151] Based on the calculated brake master cylinder pressure, a PID controller is actually added to adjust the brake master cylinder pressure. PID is a control method that inserts packaged modules during the simulation process and requires specific adjustment coefficients based on the experiment.

[0152] The preferred embodiments of the present invention are described in detail above in conjunction with the accompanying drawings. However, the scope of protection of the present invention is not limited to the specific details of the above embodiments. Within the technical concept of the present invention, any technician familiar with the technical field can make equivalent replacements or changes based on the technical solution and inventive concept of the present invention within the technical scope disclosed by the present invention. These simple variations all fall within the scope of protection of the present invention.

Claims

1. Emergency braking control strategy based on safety distance model, characterized by: The control strategy is implemented by the following steps: Step 1: Establish a three-level safety distance model: The AEB system is designed with three levels of braking control based on length and distance. The first-level partial braking distance is the driver's braking distance during normal emergency braking at the 50th percentile driver's deceleration value, the second-level partial braking distance is the shortest driver braking distance at the maximum braking deceleration, and the third-level full braking distance is the shortest vehicle braking distance at the maximum braking deceleration. Under CCRs working conditions, the first-level partial braking safety distance is calculated as follows: Under CCRs working conditions, the secondary partial braking safety distance is calculated as follows: Under CCRs conditions, the third-level full braking safety distance is calculated as follows: Under CCRm working condition, the first-stage partial braking safety distance is calculated as follows: Under CCRm working condition, the secondary partial braking safety distance is calculated as follows: Under the CCRm condition, the third-level full braking safety distance is calculated as follows: Under the CCRb1 working condition, the first-stage partial braking safety distance is calculated as follows: Under the CCRb1 working condition, the secondary partial braking safety distance is calculated as follows: Under the CCRb1 working condition, the third-level full braking safety distance is calculated as follows: Under CCRb2 working condition, the first-stage partial braking safety distance is calculated as follows: Under the CCRb2 working condition, the secondary partial braking safety distance is calculated as follows: Under the CCRb2 working condition, the third-level full braking safety distance is calculated as follows: Among them, v1 is the vehicle speed (m / s), v obj is the target vehicle speed (m / s), v rel is the relative speed of the two vehicles (m / s), a obj is the target vehicle deceleration (m / s 2 ), a b_m is the maximum deceleration (m / s 2 ), a b_50％ The acceptable braking deceleration for the 50th percentile driver (m / s 2 ), a rel_m =a b_m -a obj ,a rel_50％ =a b_50％ -a obj , t b is the braking delay time, t1 is the driver's reaction time, d x_0 is the safe stopping distance and {x|x∈c,g,r}, where c represents a conservative driver, g represents a normal driver, and r represents an aggressive driver; Step 2: Develop a hierarchical control strategy: Situations greater than the first-level partial braking safety distance are classified as safe, and the AEB system does not need to intervene at this time; situations less than the first-level partial braking safety distance and greater than the second-level partial braking safety distance are classified as first-level danger, and the AEB system is required to perform first-level partial braking according to the set first-level partial braking deceleration; situations less than the second-level partial braking safety distance and greater than the third-level full braking safety distance are classified as second-level danger, and the AEB system is required to perform second-level partial braking according to the set second-level partial braking deceleration; situations less than the third-level full braking safety distance are classified as third-level danger, and the AEB system is required to perform full braking according to the set full braking deceleration; Step 3: converting the braking deceleration determined by the AEB system in step 2 into a brake master cylinder pressure and applying it to the vehicle; The brake master cylinder pressure P b Calculate as follows: F b =K b P b Among them, K b Indicates the ratio of braking force to brake master cylinder pressure, F b is the braking force of the vehicle brake, calculated as follows: Ma exp =F b +∑F Where M represents the vehicle mass, a exp represents the expected deceleration, i.e., the braking deceleration determined by the AEB system in step 3. ∑F represents the driving resistance of the vehicle when not braking, which is calculated as follows: Where A represents the frontal area of ​​the vehicle, C D represents the air resistance coefficient, ρ represents the air density, v represents the vehicle speed, g represents the acceleration due to gravity, and f represents the rolling resistance coefficient.

2. The emergency braking control strategy based on the safety distance model according to claim 1 is characterized in that: In step 2, for a conservative driver, the AEB system performs a partial braking deceleration of a. c_par Select 2.8m / s 2 , deceleration a of the secondary partial braking c_part2 Select 5.7m / s 2 , deceleration a of full braking c_max Select 8m / s 2 ; For a normal driver, the AEB system performs a partial braking deceleration of g_part1 Select 3.7m / s 2 , deceleration a of the secondary partial braking g_part2 Select 6.5m / s 2 , deceleration a of full braking g_max Select 8m / s 2 ; For aggressive drivers, the AEB system performs partial braking at a deceleration of r_part Select 4.1m / s 2 , deceleration a of the secondary partial braking r_part2 Select 7m / s 2 , deceleration a of full braking r_max Select 8m / s 2 .

3. The emergency braking control strategy based on the safety distance model according to claim 1 is characterized in that: In the step three, the master brake cylinder pressure is adjusted by a PID controller according to the obtained master brake cylinder pressure.

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